Impaired Intestinal Permeability of Tricellular Tight Junctions in Patients with Irritable Bowel Syndrome with Mixed Bowel Habits (IBS-M)

Effects of Spirulina (Arthrospira) platensis supplementation on intestinal permeability, antioxidant and inflammatory markers, quality of life and disease severity in patients with constipated-predominant irritable bowel syndrome: a randomized double‑blind, placebo‑controlled trial

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic, functional gastrointestinal disorder (FGID) which is characterized by chronic pain related to defecation and alteration in GI motility. Recent findings indicated that intestinal barrier dysfunction, hyperpermeability, oxidative stress, and inflammation play a role in IBS pathogenesis. Considering the antioxidant properties of Spirulina (Arthrospira) platensis (SP), this study aimed to investigate the effect of SP supplementation on Quality of life (QoL), disease severity, antioxidant capacity, oxidative stress index and intestinal permeability in constipation-dominant IBS (IBS-C) patients.

METHODS

This study was a parallel randomized, double-blind, placebo-controlled clinical trial involving 60 IBS-C patients aged 18-50 years. The patients were given either 1 g SP (two capsules/day; each capsule contained 500 mg of SP) or placebo for 12 weeks. IBS-QoL, IBS-Severity system score (IBS-SSS), plasma total antioxidant capacity (TAC), malondialdehyde (MDA), and zonulin levels were measured at baseline and the end of the intervention. Univariate comparison and intention-to-treat (ITT) were used for analysis.

RESULTS

SP supplementation compared to placebo resulted in a significant increase in QoL score (7.05 ± 2.02 vs. - 1.57 ± 2.49; p = 0.008), TAC (145.27 ± 30.77 vs. -54.90 ± 45.72; p < 0.001) and decrease in IBS-SSS (-32.17 ± 8.96 vs. 1.07 ± 8.49; p = 0.002), MDA level (- 11.61 ± 2.57 vs. - 2.00 ± 2.24; p < 0.001) and zonulin level (- 0.22 ± 0.05 vs. 0.12 ± 0.07; p = 0.001). These results remained significant after adjusting for baseline values.

CONCLUSIONS

SP supplementation demonstrated a promising effect in the management of IBS. However, larger trials with a dose-dependent approach in IBS-C and other subtypes of IBS are warranted.

TRIAL REGISTRATION

The study protocol was approved by the ethical committee at the Isfahan University of Medical Sciences (Registration No. IR.MUI.

RESEARCH

REC.1401.370) and registered online at http://www.IRCT.ir (code: IRCT20140208016529N8, approved date 25.04.2023).

Association of rotating shift work with incident irritable bowel syndrome: a large population-based prospective cohort study

Objectives

Limited epidemiological study has examined the association between rotating shift work and risk of irritable bowel syndrome (IBS). This study aimed to investigate the association between shift work and risk of IBS and explore the potential mediating factors for the association.

Methods

A total of 268,290 participants from the UK Biobank were included. Cox proportional hazards model was used to examine the associations between shift work and the incidence of IBS. The mediation analyses were performed to investigate the mediating effects.

Results

Participants engaged in always/usually shift work showed a significantly increased risk of developing IBS (HR: 1.12, 95% CI: 1.03-1.23). Joint analysis indicated that, participants with both always/usually shift work and inadequate sleep duration had a 54% increased risk of IBS (HR: 1.54, 95% CI: 1.35-1.82) compared to those with adequate sleep duration and never/rarely shift work; while participants with both always/usually shift work and insomnia-always had a 65% increased risk of IBS (HR: 1.65, 95% CI: 1.43-1.90) compared to those with never/rarely shift work and never/sometimes insomnia. Mediation analysis revealed that sleep quality and anxiety/depression partially mediated the relationship between shift work and IBS incidence, contributing 16.1% (6.8-25.4%) and 3.6% (0.4-6.8%) of the mediation effect, respectively.

Conclusion

This study found that participants with always/usually shiftwork status had significantly increased risk of IBS, and this association may partially be mediated by anxiety/depression and sleep quality. Moreover, inadequate sleep duration and usually insomnia may intensify the effect of rotating shift work on the risk of incident IBS.

Mapping Research Trends on Intestinal Permeability in Irritable Bowel Syndrome with a Focus on Nutrition: A Bibliometric Analysis

Irritable Bowel Syndrome (IBS) is a complex gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits, often linked to disruptions in intestinal barrier function. Increased intestinal permeability plays a key role in IBS pathogenesis, affecting immune responses, gut microbiota, and inflammation. This study conducts a bibliometric analysis to explore global research trends on intestinal permeability in IBS, focusing on key contributors, collaboration networks, and thematic shifts, particularly the interplay between the intestinal barrier, gut microbiota, and dietary components. A total of 411 articles were retrieved from Scopus, with 232 studies analyzed using Bibliometrix in R. To optimize screening, ASReview, a machine learning tool, was employed, utilizing the Naïve Bayes algorithm combined with Term Frequency-Inverse Document Frequency (TF-IDF) for adaptive ranking of articles by relevance. This approach significantly improved screening step efficacy. The analysis highlights growing research interest, with China and the USA as leading contributors. Key themes include the role of gut microbiota in modulating permeability, the impact of dietary components (fiber, probiotics, bioactive compounds) on tight junction integrity, and the exploration of therapeutic agents. Emerging studies suggest integrating gut barrier modulation with nutritional and microbiome-targeted strategies for IBS management. This study provides a comprehensive overview of research on intestinal permeability in IBS, mapping its evolution and identifying major trends. By highlighting key contributors and thematic areas, it offers insights to guide future investigations into the interplay between gut permeability, diet, and microbiota, advancing understanding of IBS pathophysiology and management.

The Role of Gut Microbiome in Irritable Bowel Syndrome: Implications for Clinical Therapeutics

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder (FGID) characterized by chronic or recurrent gastrointestinal symptoms without organic changes, and it is also a common disorder of gut-brain interaction (DGBIs).. The symptoms of IBS not only affect the quality of life for individual patients but also place a significant burden on global healthcare systems. The lack of established and universally applicable biomarkers for IBS, along with the substantial variability in symptoms and progression, presents challenges in developing effective clinical treatments. In recent years, preclinical and clinical studies have linked the pathogenesis of IBS to alterations in the composition and function of the intestinal microbiota. Within the complex microbial community of the gut, intricate metabolic and spatial interactions occur among its members and between microbes and their hosts. Amid the multifaceted pathophysiology of IBS, the role of intestinal microenvironment factors in symptom development has become more apparent. This review aims to delve into the changes in the composition and structure of the gut microbiome in individuals with IBS. It explores how diet-mediated alterations in intestinal microbes and their byproducts play a role in regulating the pathogenesis of IBS by influencing the "brain-gut" axis, intestinal barrier function, immune responses, and more. By doing so, this review seeks to lay a theoretical foundation for advancing the development of clinical therapeutics for IBS.

Selective Uptake Into Inflamed Human Intestinal Tissue and Immune Cell Targeting by Wormlike Polymer Micelles

Inflammatory bowel disease (IBD) has become a globally prevalent chronic disease with no causal therapeutic options. Targeted drug delivery systems with selectivity for inflamed areas in the gastrointestinal tract promise to reduce severe drug-related side effects. By creating three distinct nanostructures (vesicles, spherical, and wormlike micelles) from the same amphiphilic block copolymer poly(butyl acrylate)-block-poly(ethylene oxide) (PBA-b-PEO), the effect of nanoparticle shape on human mucosal penetration is systematically identified. An Ussing chamber technique is established to perform the ex vivo experiments on human colonic biopsies, demonstrating that the shape of polymeric nanostructures represents a rarely addressed key to tissue selectivity required for efficient IBD treatment. Wormlike micelles specifically enter inflamed mucosa from patients with IBD, but no significant uptake is observed in healthy tissue. Spheres (≈25 nm) and vesicles (≈120 nm) enter either both normal and inflamed tissue types or do not penetrate any tissue. According to quantitative image analysis, the wormlike nanoparticles localize mainly within immune cells, facilitating specific targeting, which is crucial for further increasing the efficacy of IBD treatment. These findings therefore demonstrate the untapped potential of wormlike nanoparticles not only to selectively target the inflamed human mucosa, but also to target key pro-inflammatory cells.

Gut microbiota and intestinal immunity-A crosstalk in irritable bowel syndrome

Irritable bowel syndrome (IBS), one of the most prevalent functional gastrointestinal disorders, is characterized by recurrent abdominal pain and abnormal defecation habits, resulting in a severe healthcare burden worldwide. The pathophysiological mechanisms of IBS are multi-factorially involved, including food antigens, visceral hypersensitivity reactions, and the brain-gut axis. Numerous studies have found that gut microbiota and intestinal mucosal immunity play an important role in the development of IBS in crosstalk with multiple mechanisms. Therefore, based on existing evidence, this paper elaborates that the damage and activation of intestinal mucosal immunity and the disturbance of gut microbiota are closely related to the progression of IBS. Combined with the application prospect, it also provides references for further in-depth exploration and clinical practice.

The Effect of Inflammatory Bowel Disease and Irritable Bowel Syndrome on Pravastatin Oral Bioavailability: In vivo and in silico evaluation using bottom-up wbPBPK modeling

The common disorders irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) can modify the drugs' pharmacokinetics via their induced pathophysiological changes. This work aimed to investigate the impact of these two diseases on pravastatin oral bioavailability. Rat models for IBS and IBD were used to experimentally test the effects of IBS and IBD on pravastatin pharmacokinetics. Then, the observations made in rats were extrapolated to humans using a mechanistic whole-body physiologically-based pharmacokinetic (wbPBPK) model. The rat in vivo studies done herein showed that IBS and IBD decreased serum albumin (> 11% for both), decreased PRV binding in plasma, and increased pravastatin absolute oral bioavailability (0.17 and 0.53 compared to 0.01) which increased plasma, muscle, and liver exposure. However, the wbPBPK model predicted muscle concentration was much lower than the pravastatin toxicity thresholds for myotoxicity and rhabdomyolysis. Overall, IBS and IBD can significantly increase pravastatin oral bioavailability which can be due to a combination of increased pravastatin intestinal permeability and decreased pravastatin gastric degradation resulting in higher exposure. This is the first study in the literature investigating the effects of IBS and IBD on pravastatin pharmacokinetics. The high interpatient variability in pravastatin concentrations as induced by IBD and IBS can be reduced by oral administration of pravastatin using enteric-coated tablets. Such disease (IBS and IBD)-drug interaction can have more drastic consequences for narrow therapeutic index drugs prone to gastric degradation, especially for drugs with low intestinal permeability.

The Variability of Tryptophan Metabolism in Patients with Mixed Type of Irritable Bowel Syndrome

Patients with a mixed type of irritable bowel syndrome (IBS-M) experience constipation and diarrhea, which alternate between weeks or months. The pathogenesis of this syndrome is still little understood. The aim of the study was mainly to evaluate the urinary excretion of selected tryptophan (TRP) metabolites during the constipation and diarrhea periods of this syndrome. In 36 patients with IBS-M and 36 healthy people, serum serotonin level was measured by ELISA and urinary levels of 5-hydroxyindoleacetic acid (5-HIAA), kynurenine (KYN) and indican (3-IS) were determined using the LC-MS/MS method. The levels of all above metabolites were higher in the patient group, and increased significantly during the diarrheal period of IBS-M. In particular, the changes concerned 5-HIAA (3.67 ± 0.86 vs. 4.59 ± 0.95 mg/gCr, p < 0.001) and 3-IS (80.2 ± 17.4 vs. 93.7 ± 25.1 mg/g/Cr, p < 0.001). These changes coexisted with gut microbiome changes, assessed using hydrogen-methane and ammonia breath tests. In conclusion, the variability of TRP metabolism and the gut microbiome may cause the alternation of IBS-M symptoms.

Intestinal Membrane Function in Inflammatory Bowel Disease

Inflammatory bowel disease is a set of chronic inflammatory diseases that mainly develop in the gastrointestinal mucosa, including ulcerative colitis and Crohn's disease. Gastrointestinal membrane permeability is an important factor influencing the pharmacological effects of pharmaceuticals administered orally for treating inflammatory bowel disease and other diseases. Understanding the presence or absence of changes in pharmacokinetic properties under a disease state facilitates effective pharmacotherapy. In this paper, we reviewed the gastrointestinal membrane function in ulcerative colitis and Crohn's disease from the perspective of in vitro membrane permeability and electrophysiological parameters. Information on in vivo permeability in humans is summarized. We also overviewed the inflammatory bowel disease research using gut-on-a-chip, in which some advances have recently been achieved. It is expected that these findings will be exploited for the development of therapeutic drugs for inflammatory bowel disease and the optimization of treatment options and regimens.

Epithelial Barrier Dysfunction in Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D) via Downregulation of Claudin-1

BACKGROUND

In patients with diarrhea-predominant irritable bowel syndrome (IBS-D), the diarrheal mechanisms are largely unknown, and they were examined in this study on colon biopsies.

METHODS

Electrophysiological measurements were used for monitoring functional changes in the diarrheic colon specimens. In parallel, tight junction protein expression was analyzed by Western blot and confocal laser-scanning microscopy, and signaling pathway analysis was performed using RNA sequencing and bioinformatics.

RESULTS

Epithelial resistance was decreased, indicating an epithelial leak flux diarrheal mechanism with a molecular correlate of decreased claudin-1 expression, while induction of active anion secretion and impairment of active sodium absorption via the epithelial sodium channel, ENaC, were not detected. The pathway analysis revealed activation of barrier-affecting cytokines TNF-α, IFN-γ, IL-1β and IL-4.

CONCLUSIONS

Barrier dysfunction as a result of epithelial tight junction changes plays a role in IBS-D as a pathomechanism inducing a leak flux type of diarrhea.

Myrrh protects against IL-13-induced epithelial barrier breakdown in HT-29/B6 cells

The oleoresin myrrh has been used for centuries as an anti-inflammatory remedy for a variety of diseases and is said to have a protective effect on the intestinal epithelium. An intact epithelial barrier function is the prerequisite for a healthy gut. Inflammatory and infectious diseases of the intestine, in particular, lead to barrier impairment resulting in leak-flux diarrhea and mucosal immune responses. Therefore, the aim of the present study was to investigate the protective effect of myrrh in an experimental inflammatory situation, namely, under the influence of IL-13, one of the key cytokines in ulcerative colitis. We used human intestinal epithelial HT-29/B6 cell monolayers for functional and molecular assessment of the epithelial barrier under IL-13 and myrrh treatment. IL-13 induced a loss in barrier function that was fully restored with myrrh treatment, as shown by transepithelial electrical resistance measurements. The molecular correlate of the IL-13-mediated barrier dysfunction could be assigned to an upregulation of the channel-forming tight junction (TJ) protein claudin-2 and to a subcellular redistribution of the TJ protein tricellulin, loosening the sealing of tricellular TJs. Moreover, IL-13 exposure leads to an increase in the number of apoptotic cells, contributing to the leak pathway of barrier dysfunction. Myrrh protected against changes in TJ deregulation and decreased the elevated apoptotic ratio under IL-13. The protective effects are mediated through the inhibition of the STAT3 and STAT6 pathway. In conclusion, our results demonstrate that myrrh exhibits antagonizing effects against IL-13-induced barrier impairment in a human intestinal cell model. These data suggest the use of myrrh as a promising option in the treatment of inflammatory bowel disease.

The epithelial barrier: The gateway to allergic, autoimmune, and metabolic diseases and chronic neuropsychiatric conditions

Since the 1960 s, our health has been compromised by exposure to over 350,000 newly introduced toxic substances, contributing to the current pandemic in allergic, autoimmune and metabolic diseases. The "Epithelial Barrier Theory" postulates that these diseases are exacerbated by persistent periepithelial inflammation (epithelitis) triggered by exposure to a wide range of epithelial barrier-damaging substances as well as genetic susceptibility. The epithelial barrier serves as the body's primary physical, chemical, and immunological barrier against external stimuli. A leaky epithelial barrier facilitates the translocation of the microbiome from the surface of the afflicted tissues to interepithelial and even deeper subepithelial locations. In turn, opportunistic bacterial colonization, microbiota dysbiosis, local inflammation and impaired tissue regeneration and remodelling follow. Migration of inflammatory cells to susceptible tissues contributes to damage and inflammation, initiating and aggravating many chronic inflammatory diseases. The objective of this review is to highlight and evaluate recent studies on epithelial physiology and its role in the pathogenesis of chronic diseases in light of the epithelial barrier theory.

Predictive Potential of Biomarkers of Intestinal Barrier Function for Therapeutic Management with Teduglutide in Patients with Short Bowel Syndrome

INTRODUCTION

The human intestinal tract reacts to extensive resection with spontaneous intestinal adaptation. We analyzed whether gene expression analyses or intestinal permeability (IP) testing could provide biomarkers to describe regulation mechanisms in the intestinal barrier in short bowel syndrome (SBS) patients during adaptive response or treatment with the glucagon-like peptide-2 analog teduglutide.

METHODS

Relevant regions of the GLP-2 receptor gene were sequenced. Gene expression analyses and immunohistochemistry were performed from mucosal biopsies. IP was assessed using a carbohydrate oral ingestion test.

RESULTS

The study includes 59 SBS patients and 19 controls. Increases in gene expression with teduglutide were received for sucrase-isomaltase, sodium/glucose cotransporter 1, and calcium/calmodulin serine protein kinase. Mannitol recovery was decreased in SBS but elevated with teduglutide (Δ 40%), showed a positive correlation with remnant small bowel and an inverse correlation with parenteral support.

CONCLUSIONS

Biomarkers predicting clinical and functional features in human SBS are very limited. Altered specific gene expression was shown for genes involved in nutrient transport but not for genes controlling tight junctions. However, mannitol recovery proved useful in describing the absorptive capacity of the gut during adaptation and treatment with teduglutide.

The Role of Ion Channels in Functional Gastrointestinal Disorders (FGID): Evidence of Channelopathies and Potential Avenues for Future Research and Therapeutic Targets

Several gastrointestinal (GI) tract abnormalities, including visceral hypersensitivity, motility, and intestinal permeability alterations, have been implicated in functional GI disorders (FGIDs). Ion channels play a crucial role in all the functions mentioned above. Hormones and natural molecules modulate these channels and represent targets of drugs and bacterial toxins. Mutations and abnormal functional expression of ion channel subunits can lead to diseases called channelopathies. These channelopathies in gastroenterology are gaining a strong interest, and the evidence of co-relationships is increasing. In this review, we describe the correlation status between channelopathies and FGIDs. Different findings are available. Among others, mutations in the ABCC7/CFTR gene have been described as a cause of constipation and diarrhea. Mutations of the SCN5A gene are instead associated with irritable bowel syndrome. In contrast, mutations of the TRPV1 and TRPA genes of the transient receptor potential (TRP) superfamily manifest hypersensitivity and visceral pain in sensory nerves. Recently, mice and humans affected by Cantu syndrome (CS), which is associated with the mutations of the KCNJ8 and ABCC9 genes encoding for the Kir6.1 and SUR2 subunits, showed dysfunction of contractility throughout the intestine and death in the mice after the weaning on solid food. The discovery of a correlation between channelopathies and FIGD opens new avenues for discovering new direct drug targets for specific channelopathies, leading to significant implications for diagnosing and treating functional GI diseases.

Paracellular permeability and tight junction regulation in gut health and disease

Epithelial tight junctions define the paracellular permeability of the intestinal barrier. Molecules can cross the tight junctions via two distinct size-selective and charge-selective paracellular pathways: the pore pathway and the leak pathway. These can be distinguished by their selectivities and differential regulation by immune cells. However, permeability increases measured in most studies are secondary to epithelial damage, which allows non-selective flux via the unrestricted pathway. Restoration of increased unrestricted pathway permeability requires mucosal healing. By contrast, tight junction barrier loss can be reversed by targeted interventions. Specific approaches are needed to restore pore pathway or leak pathway permeability increases. Recent studies have used preclinical disease models to demonstrate the potential of pore pathway or leak pathway barrier restoration in disease. In this Review, we focus on the two paracellular flux pathways that are dependent on the tight junction. We discuss the latest evidence that highlights tight junction components, structures and regulatory mechanisms, their impact on gut health and disease, and opportunities for therapeutic intervention.